Frog of the Week

Southern Mountain Yellow-Legged Frog (Rana muscosa)

Southern Mountain Yellow-Legged Frog
photo by Chris Brown (USGS)
Conservation status is Endangered

Common Name: Southern Mountain Yellow-Legged Frog
Scientific Name: Rana muscosa
Family: Ranidae – True Frog family
Locations: United States – California
Size: 2 – 3 inches (5 – 7.6 cm)

The International Union for the Conservation of Nature (IUCN) Red List and the United States federal government categorizes the Southern Mountain Yellow-Legged Frog as an endangered species. They live in only a few small areas in southeastern California near the Sierra Nevada Mountains. It was not always like this. They used to be a common species before they started to disappear.

There are many reasons for the declines. Trout was introduced into the Sierra Nevada Mountains to increase recreational fishing there. These non-native trout eat on the tadpoles of the frog as they are predators. Studies shown that removing trout from lakes in the Southern Mountain Yellow-Legged Frog’s habitat allows the frog repopulate the area and increase numbers.

Southern Mountain Yellow-Legged Frog
photo by William Flaxington

Another key reason for the population decline of the Southern Mountain Yellow-Legged Frog is the introduction of Chytrid Fungus into their environment. Chytrid Fungus is a deadly pathogen that thickens the skin of the frog. The thicker skin prevents the ability of the frog to breathe and drink through its skin and eventually causes death. The disease has lead to widespread deaths of amphibians all over the world. Sadly, it has also affected the Mountain Yellow-Legged Frog. Those are the two main reasons for the decline but other reasons include pesticides, climate change, habitat degradation and fragmentation, and drought.

Hope for the Southern Mountain Yellow Legged Frog

Luckily, zoos are trying to help the species. The San Diego Zoo has been captive breeding the Southern Mountain Yellow-legged Frog and releasing the tadpoles into the wild. The Oakland Zoo and the San Francisco Zoo have been catching juvenile frogs and raising them in captivity. They give the frogs anti-fungal baths and when they are older, they release them.

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